The advantage of the kites they demonstrate here is that they leave the deck of the boat much more free for cargo than traditional sails. There have been a few 'low footprint' wind power startups for shipping but from the purely financial perspective the lost cargo volume has never yet been worth the fuel savings. Using a kite that consumes no cargo capacity could actually help an eco-technology be adopted by these shipping companies if it helps their bottom line.
Sure, make fun of it, but sails are not the same as kites.
With modern tech they might be able to make kites that are truly enormous, way bigger than the sails that are limited by the size of the mast. In addition, the kites can be raised into different winds than the ones at the surface.